1. Field of the Invention
The present invention relates to a resonance coil, an electric power transmission device, an electric power receiving device, and an electric power transmission system.
2. Description of Related Art
Recently, hybrid vehicles and electric vehicles that use electric power from batteries to drive driving wheels are receiving much attention in environmental consciousness.
In recent years in particular, for electrically driven vehicles that are equipped with the battery described above, wireless charging that can charge the battery without using a plug but in a noncontact manner receives attention. More recently, various types of charging method are proposed for the wireless charging method. Particularly, a technique that transmits electric power in the noncontact manner by utilizing a resonance phenomenon attracts lots of attention.
For example, a vehicle and a power supply device that are disclosed in Japanese Patent Application Publication No. 2010-73976 (JP-A-2010-73976) include a communication coil, respectively. The communication coil that is installed in the vehicle includes a resonance coil and a power receiving coil, and the communication coil that is installed in the power supply device includes a resonance coil and a power supply coil. Noncontact transmission of electric power is performed between the resonance coil that is installed in the power supply device and the resonance coil that is installed in the vehicle by utilizing the resonance phenomenon.
On page 11, Proceedings of Communication Vol. 1, 2010 IEICE Society Conference, entitled “A Study on Antenna Shape for Electro-Magnetic Resonant Type Wireless Power Transmission System” by Masafumi Kadoi, Nobuyoshi Kikuma, Hiroshi Hirayama, and Kunio Sakakibara, the resonance coil that is focused on prevention of deterioration of electric power transmission efficiency even if the resonance coil for electric power transmission and the resonance coil for electric power reception are misaligned is proposed.
In addition, as disclosed in Japanese Patent Application Publication No. 2003-79597 (JP-A-2003-79597), imaging devices such as a magnetic resonance imaging (MRI) that utilize a nuclear magnetic resonance phenomenon to achieve imaging of cross sections of body are known.
In the resonance coil that is disclosed in JP-A-2010-73976, if the resonance coil that is installed on the vehicle-side and the resonance coil on an equipment-side are misaligned, the transmission efficiency of electric power deteriorates significantly.
In the resonance coil that is disclosed in the aforementioned “A Study on Antenna Shape for Electro-Magnetic Resonant Type Wireless Power Transmission System,” a coil wire that forms the resonance coil has an overlapping section in a height direction. In the overlapping section in the coil wire, coil wires need to have specific distances in the height direction in order to secure insulation properties between the coil wires. As a result, the resonance coil thickens in the height direction.
Briefly describing, the nuclear magnetic resonance phenomenon that the imaging device disclosed in JP-A-2003-79597 utilizes is the phenomenon such that when hydrogen atoms in water are subjected to magnetism, the hydrogen atoms resonate to generate signals. Because amount of water (amount of hydrogen atoms) varies depending on parts and organs in human body, the MRI irradiates magnetic fields in the human body, receives the signals that are generated by the aforementioned nuclear magnetic resonance phenomenon as appropriate, and creates cross-sectional images of human body based on received signals.
As described above, the nuclear magnetic resonance phenomenon that the MRI or the like utilizes and an electromagnetic resonant coupling that is utilized in transmission and reception of electric power use different phenomena from each other, and the structures differ entirely.